Electrical workers often have to work on electrical lines, and they need to ensure that the line is not hot or live. Thus, it becomes prudent and necessary to test whether a line is hot before work commences. An electrical worker will use a non-contact voltage (“NCV”) detector to test whether the line is hot. These non-contact voltage detectors are useful because touching the line is not necessary in order to tell the voltage status of the line. However, non-contact voltage detectors can suffer from failures that may yield dangerous false negative results. For example, non-contact voltage detectors may have weak batteries, shorted or open LED indicators, faulty buzzers, or broken wiring at the probe. Conventional non-contact voltage detectors fail to detect many of these fault conditions, resulting in potentially unsafe working conditions for electrical workers.